**5.2 Disadvantages of OGTT**

*5.2.1 Factors why OGTT may not be the first choose in screening for dysglycaemia*


more between 90 and 180 minutes post-glucose solution ingestion. It is possible therefore that some of the earlier reports of poor reproducibility of the test may be attributable to a volume effect. The gastric emptying falls as the glucose concentration rises and this was demonstrated over a wide range of glucose concentrations [77]. It has been suggested that this is due to the stimulation of receptors in the duodenum sensitive to the osmotic pressure of the duodenal contents. The rate for gastric emptying in normal individuals lies between 40 and 80 minutes. Chronic pancreatitis does, however, causes overt diabetes in some patients, and most patients with this condition have impaired insulin secretion [78] even if this is not sufficiently severe to produce disturbances in carbohydrate tolerance. The liver, situated between the portal and systemic circulation, is in a position to influence oral glucose tolerance profoundly. Reproducibility can be improved by drawing Blood at the stipulated time or at least within 5 minutes and centrifuge sample

*Oral Glucose Tolerance Test (OGTT): Undeniably the First Choice Investigation…*

e. Other factors are: Lack of adequate patient

j. Others are: gastric emptying, Intestinal absorption, the gastrointestinal hormonal stimulus to insulin release, the liver, and the pancreatic islets.

f. Exercise during the days before the test g. Caffeine use, Smoking, Medications, Stress h. Changed in ambient temperature i. Volume of the glucose solution

preparations, Diet

To improve the reliability of a test it should be conducted in the individual that appropriately require the test, hence OGTT reproducibility can be improved when

Interaction with patients before procedure is very important because one of the

resistance 14. Hypertension 15. Recurrent infections

disease).

11. Women with polycystic ovarian disease

12. Woman who delivered a macrosomic baby(>4 kg) 13. Have other clinical conditions associated with insulin

16. It also helps determine if there is other condition that affects blood glucose levels (e.g., Cushing's syndrome,

celiac disease, cystic fibrosis, acromegaly, pheochromocytoma, hemochromatosis, or Wilson's

conditions leading to spurious result in patient investigation is lack of patient's

within 45 minutes of drawing it to obtain plasma.

1. Age > 45 yrs. (type 2 among 40-70 yr —7%, IGT—20%. In general pop—

2. Body Mass Index(BMI) >27 kg/m2 3. High risk ethnic groups—Africans,

4. Family history(first-degree relatives (increase risk by 2–4 fold 5. High waist circumference(>92 cm,

7. History of gestational diabetes mellitus 8. Previous evidence of IGT or IFG 9. Dyslipidaemia(decrease HDL and

10. Patient with Cardiovascular disease

Carribeans, Asians

4.3%

>80 cm) 6. Sedentary lifestyle

increase TGs)

*Indications for OGTT.*

**Table 4.**

**125**

a. The OGTT is a non-physiological procedure and the interperson variability is rather high.

*DOI: http://dx.doi.org/10.5772/intechopen.96549*

d. Biological variation is been found to be up to 20–35%—these can be minimized by stringent careful attention to the protocol

b. Analytical and biological variability c. Use of different samples(eg; venous and capillary for a repeat or during same

*Causes of variability in OGTT results.*

procedure

**Table 3.**

it is conducted in the selected individuals noted in **Table 4**.

*5.2.2 Patient's preparation for conduct of OGTT, improving reproducibility*


Due to the number of limitations, the OGTT should be undertaken on two separate occasions before the results are considered abnormal (unless the initial results are grossly abnormal). It has high intra-and interperson variability. This may be due to a number of factors, including diet and exercise during the days before the test, caffeine use, smoking, medications, and stress. However, with careful patient preparation the impact of these modifiable factors can be markedly reduced resulting in improved reproducibility. These modifiable factors can be placed into three categories:


This shows that with proper patient preparations spanning through history taking and physical examination and appropriate patient education will highly improve the reproducibility of OGTT, hence care must be taken of the factors [65, 77] in **Table 3** during patient preparation.

An increase in the volume or decrease in the osmolality of a meal may result in an increase in the rate of gastric emptying and in a subsequent increase in glycaemia. Gastric emptying has implications for the reproducibility of the OGTT. It was twice observed that the faster an OGTT meal is emptied from the stomach, the higher the resulting postprandial glycaemia level. About 30%, 19.8% and 14% differences in postprandial glucose after the dilution of 75-g (present study), 50-g and 25-g tolerance tests was noted, respectively [77]. The dilution effect is noted

*Oral Glucose Tolerance Test (OGTT): Undeniably the First Choice Investigation… DOI: http://dx.doi.org/10.5772/intechopen.96549*


**Table 3.**

individual undergoing OGTT. Finally, all trials aimed at type 2 diabetes prevention included IGT subjects [74, 75], who could not be possibly recognised without OGTT, seems therefore evident that the routine execution of OGTT is presently the

*5.2.1 Factors why OGTT may not be the first choose in screening for dysglycaemia*

a. Biological variation which may account for about 5.7% of available blood

c. More cost and time, Cumbersome, unfriendly procedure for patients

d. Because of the OGTT's high variability and low sensitivity, epidemiological studies based on a single OGTT may overestimate the prevalence of diabetes

Due to the number of limitations, the OGTT should be undertaken on two separate occasions before the results are considered abnormal (unless the initial results are grossly abnormal). It has high intra-and interperson variability. This may be due to a number of factors, including diet and exercise during the days before the test, caffeine use, smoking, medications, and stress. However, with careful patient preparation the impact of these modifiable factors can be markedly reduced resulting in improved reproducibility. These modifiable factors can be placed into

a. When preparing patient for test: duration of fast; prior carbohydrate intake; medications (e.g. thiazide, oral contraceptives and corticosteroids); trauma;

b. Glucose given: quantity of glucose ingested; volume of administration; and

c. Fasting sample: posture; anxiety; caffeine; smoking; physical activity; stress,

This shows that with proper patient preparations spanning through history taking and physical examination and appropriate patient education will highly improve the reproducibility of OGTT, hence care must be taken of the factors

An increase in the volume or decrease in the osmolality of a meal may result in

glycaemia. Gastric emptying has implications for the reproducibility of the OGTT. It was twice observed that the faster an OGTT meal is emptied from the stomach, the higher the resulting postprandial glycaemia level. About 30%, 19.8% and 14% differences in postprandial glucose after the dilution of 75-g (present study), 50-g and 25-g tolerance tests was noted, respectively [77]. The dilution effect is noted

an increase in the rate of gastric emptying and in a subsequent increase in

intercurrent illness; age; physical activity.

[65, 77] in **Table 3** during patient preparation.

b. Variable effects of administration of hyperosmolar glucose solution on gastric emptying, eg, nausea, vomiting, osmotic diarrhea, abdominal distension. Flavoring with sugar-free lemon and chilling increases palatability and may

one and only possible answer (Undeniably) [76].

*Type 2 Diabetes - From Pathophysiology to Cyber Systems*

**5.2 Disadvantages of OGTT**

glucose value

reduce nausea.

by as much as 16%

rate of ingestion.

and time of the day

three categories:

**124**

*Causes of variability in OGTT results.*

more between 90 and 180 minutes post-glucose solution ingestion. It is possible therefore that some of the earlier reports of poor reproducibility of the test may be attributable to a volume effect. The gastric emptying falls as the glucose concentration rises and this was demonstrated over a wide range of glucose concentrations [77]. It has been suggested that this is due to the stimulation of receptors in the duodenum sensitive to the osmotic pressure of the duodenal contents. The rate for gastric emptying in normal individuals lies between 40 and 80 minutes. Chronic pancreatitis does, however, causes overt diabetes in some patients, and most patients with this condition have impaired insulin secretion [78] even if this is not sufficiently severe to produce disturbances in carbohydrate tolerance. The liver, situated between the portal and systemic circulation, is in a position to influence oral glucose tolerance profoundly. Reproducibility can be improved by drawing Blood at the stipulated time or at least within 5 minutes and centrifuge sample within 45 minutes of drawing it to obtain plasma.

To improve the reliability of a test it should be conducted in the individual that appropriately require the test, hence OGTT reproducibility can be improved when it is conducted in the selected individuals noted in **Table 4**.

### *5.2.2 Patient's preparation for conduct of OGTT, improving reproducibility*

Interaction with patients before procedure is very important because one of the conditions leading to spurious result in patient investigation is lack of patient's


education and preparation. Interacting with patient is important in improving reproducibility of test for the following reasons:

